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<article class='withtoc'>
    <h1>
      圆角和圆圈
      <a class="edit-page-link" href="https://github.com/liaohuqiu/fresco-docs-cn/blob/docs/docs/01-rounded-corners-and-circles.md" target="_blank">编辑和纠错</a>
    </h1>
    <p></p>

    <p>Drawee 轻松支持圆角显示，并且显示圆角时，并不复制和修改Bitmap对象，那样太耗费内存。</p>

<h3>圆角</h3>

<p>圆角实际有2中呈现方式:</p>

<ol>
<li>圆圈 - 设置<code>roundAsCircle</code>为true</li>
<li>圆角 - 设置<code>roundedCornerRadius</code></li>
</ol>

<p>设置圆角时，支持4个角不同的半径。XML中无法配置，但可在Java代码中配置。</p>

<h3>设置圆角</h3>

<p>可使用以下两种方式:</p>

<ol>
<li>默认使用一个shader绘制圆角，但是仅仅占位图所要显示的图有圆角效果。失败示意图和重下载示意图无圆角效果。</li>
<li>叠加一个<code>solid color</code>来绘制圆角。但是背景需要固定成指定的颜色。
在XML中指定 <code>roundWithOverlayColor</code>, 或者通过调用<code>setOverlayColor</code>来完成此设定。</li>
</ol>

<h3>XML中配置</h3>

<p><code>SimpleDraweeView</code> 支持如下几种圆角配置:</p>
<div class="highlight"><pre><code class="language-xml" data-lang="xml"><span class="nt">&lt;com.facebook.drawee.view.SimpleDraweeView</span>
   <span class="err">...</span>
   <span class="na">fresco:roundedCornerRadius=</span><span class="s">&quot;5dp&quot;</span>
   <span class="na">fresco:roundBottomLeft=</span><span class="s">&quot;false&quot;</span>
   <span class="na">fresco:roundBottomRight=</span><span class="s">&quot;false&quot;</span>
   <span class="na">fresco:roundWithOverlayColor=</span><span class="s">&quot;@color/blue&quot;</span>
   <span class="na">fresco:roundingBorderWidth=</span><span class="s">&quot;1dp&quot;</span>
   <span class="na">fresco:roundingBorderColor=</span><span class="s">&quot;@color/red&quot;</span>
</code></pre></div>
<h3>代码中配置</h3>

<p>在创建 <a href="using-drawees-code.html">DraweeHierarchy</a> 时，可以给<code>GenericDraweeHierarchyBuilder</code>指定一个<a href="../javadoc/reference/com/facebook/drawee/generic/RoundingParams.html">RoundingParams</a> 用来绘制圆角效果。</p>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">RoundingParams</span> <span class="n">roundingParams</span> <span class="o">=</span> <span class="n">RoundingParams</span><span class="o">.</span><span class="na">fromCornersRadius</span><span class="o">(</span><span class="mi">7</span><span class="n">f</span><span class="o">);</span>
<span class="n">roundingParams</span><span class="o">.</span><span class="na">setOverlayColor</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">color</span><span class="o">.</span><span class="na">green</span><span class="o">);</span>
<span class="c1">// 或用 fromCornersRadii 以及 asCircle 方法</span>
<span class="n">genericDraweeHierarchyBuilder</span>
    <span class="o">.</span><span class="na">setRoundingParams</span><span class="o">(</span><span class="n">roundingParams</span><span class="o">);</span>
</code></pre></div>
<p>你也可以在运行时，改变圆角效果</p>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">RoundingParams</span> <span class="n">roundingParams</span> <span class="o">=</span> 
    <span class="n">mSimpleDraweeView</span><span class="o">.</span><span class="na">getHierarchy</span><span class="o">().</span><span class="na">getRoundingParams</span><span class="o">();</span>
<span class="n">roundingParams</span><span class="o">.</span><span class="na">setBorder</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">color</span><span class="o">.</span><span class="na">red</span><span class="o">,</span> <span class="mf">1.0</span><span class="o">);</span>
<span class="n">roundingParams</span><span class="o">.</span><span class="na">setRoundAsCircle</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
<span class="n">mSimpleDraweeView</span><span class="o">.</span><span class="na">getHierarchy</span><span class="o">().</span><span class="na">setRoundingParams</span><span class="o">(</span><span class="n">roundingParams</span><span class="o">);</span>
</code></pre></div>
<blockquote>
<p>在运行时，不能改变呈现方式: 原本是圆角，不能改为圆圈。</p>
</blockquote>


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